Two-Way Frequency Fluctuations Observed During Coronal Radio Sounding Experiments

Abstract

Coronal radio-sounding experiments were carried out using two-way coherent dual-frequency carrier signals of the ESA spacecraft Rosetta (ROS) in 2006. Frequency measurements recorded at both NASA and ESA tracking stations (sample rate: 1 Hz) are analyzed in this work. Spectral analysis of the S-band, X-band, and differential frequency records has shown that the mean frequency fluctuation of each signal can be described by a radial power-law function of the form σ_i=A_i(R/R_⊙)^−mi, where i=x,s,sx. The ratio of the coefficients A_s and A_x is not the expected theoretical value A_s/A_x=f_s/f_x. This occurs because the X-band fluctuations underlie a two-way propagation mode while the S-band fluctuations are essentially the product of a one-way propagation experiment. Results are compared with similar, but not identical, two-way radio propagation experiments performed during the 1991 solar conjunction of the Ulysses spacecraft.